JP2005206398A - Reformer and method of operating the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reformer in which equipment in the downstream side of the reformer is miniaturized and durability or the like is improved by lowering the temperature of a reformed gas at the outlet of the reformer while suppressing the production of methane to improve the reforming efficiency in the production of a hydrogen enriched gas by reforming a hydrocarbon-based fuel, and a method of operating the same. <P>SOLUTION: In the reformer and the method of operating the same, the reformer is constructed by alternately stacking a reforming gas passing layer 10 to which a hydrocarbon-based fuel is supplied and a combustion gas passing layer 12 to which a fuel gas is supplied. An oxidation catalyst layer 14 is provided in the middle of the gas flow direction in the combustion gas passing layer 12 to locally heat the reforming gas passing layer 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a reformer for producing hydrogen gas used for hydrogen fuel cells, hydrogenation of various organic compounds, various industrial applications, and the like, from a hydrocarbon-based raw material, and an operation method thereof.

  In recent years, fuel cells that generate electricity by electrochemical reaction between hydrogen and oxygen have attracted attention as energy sources. Hydrogen supplied to the fuel cell is generated, for example, by reforming from a hydrocarbon fuel. Examples of the reforming reaction include a steam reforming reaction using steam as an oxidizing agent, and a partial oxidation reaction using oxygen as an oxidizing agent.

  The hydrogen-rich gas produced by the steam reforming reaction is heat-exchanged by a heat exchanger as shown in FIG. 6 and adjusted to a predetermined temperature, and then a CO reduction unit equipped with a hydrogen separation membrane, a CO shift reactor, etc. The hydrogen gas is selectively extracted from the hydrogen-rich gas under a temperature condition of 200 ° C. to 600 ° C., and this hydrogen gas is supplied to the fuel cell.

  Conventionally, in such a hydrocarbon reformer, it has been required to maintain the reforming catalyst in a highly active state for a long period of time in order to efficiently produce reformed gas by the reforming catalyst. As one means for this, when the reforming catalyst reaches a predetermined set deterioration level, air is supplied to the reforming catalyst, and a regeneration operation for regenerating the reformed catalyst is performed, and then the reforming reaction operation is performed again. A method has been proposed in which the reforming reaction and the regeneration operation are repeated. (Patent Document 1)

  However, the reforming efficiency in the hydrocarbon reformer greatly affects the operation state of the reformer as well as the problem of deterioration of the reforming catalyst, and the structural state of the entire reforming system depends on the operation state of the reformer. Problems also derive.

That is, as a conventional reformer, in a reformer in which a reformed gas circulation layer to which a hydrocarbon-based fuel is supplied and a combustion gas circulation layer to which a fuel gas is supplied are alternately laminated, Increasing the reforming efficiency of the reformer increases the temperature of the reformed gas at the outlet of the reformer, which causes various problems such as an increase in the size and durability of equipment installed on the downstream side of the reformer, In order to solve these problems, when the temperature of the reformed gas at the reformer outlet is lowered, the amount of methane in the reformed gas at the reformer outlet increases and the amount of hydrogen in the reformed gas decreases. The reforming efficiency decreases.
JP-A-11-79702

  An object of the present invention is to solve the above problems. That is, the object of the present invention is to reduce the temperature of the reformed gas at the reformer outlet while suppressing the generation of methane and increasing the reforming efficiency when reforming hydrocarbon fuel to produce hydrogen rich gas. An object of the present invention is to provide a reformer that can be reduced, downsize equipment on the downstream side of the reformer, and improve durability and the operation method thereof.

That is, the present invention
<1> A reformer in which a reformed gas circulation layer to which a hydrocarbon-based fuel is supplied and a combustion gas circulation layer to which a fuel gas is supplied are alternately stacked, and the gas flow in the reformed gas circulation layer It is the reformer which provided the site | part heated locally in the middle of a direction.
According to this reformer, steam reforming (SR) reaction or partial oxidation reaction occurs in the locally heated region to improve reforming efficiency. Thus, it becomes smaller due to heat exchange with the low-temperature fuel gas before combustion, and the gas temperature at the reformer outlet becomes lower.
<2> The portion that is locally heated in the gas flow direction in the reformed gas circulation layer is provided with an oxidation catalyst layer in the gas flow direction of the combustion gas circulation layer to which fuel gas is supplied. The reformer according to <1>.
According to this reformer, the fuel gas is combusted by the oxidation catalyst, and the reformed gas circulation layer is locally heated by this combustion heat.
<3> A method of operating a reformer in which a reformed gas circulation layer to which a hydrocarbon-based fuel is supplied and a combustion gas circulation layer to which a fuel gas is supplied are alternately stacked, the reformed gas circulation layer The operation method of the reformer characterized by heating locally in the middle of the gas flow direction.
According to this reformer operation method, steam reforming (SR) reaction or partial oxidation reaction occurs in the locally heated region to improve reforming efficiency. Until the gas temperature at the reformer outlet becomes low.
<4> An oxidation catalyst layer is provided in the middle of the gas flow direction of the combustion gas circulation layer to which the fuel gas is supplied, and the middle of the gas flow direction in the reformed gas circulation layer is locally heated. The reformer operating method according to <3>.
According to this reformer operation method, the fuel gas is combusted by the oxidation catalyst, and the reformed gas circulation layer is locally heated by this combustion heat.

  According to the hydrocarbon reformer of the present invention, there is provided a reformer capable of reforming hydrocarbon fuel at low temperature while suppressing methane production at low temperature and maintaining high reforming efficiency. Can do. Further, according to the hydrocarbon fuel reforming method of the present invention, it is possible to reform the hydrocarbon fuel at a low temperature while suppressing methane production at a low temperature and maintaining a high reforming efficiency. The later heat exchanger can be unnecessary or downsized, resulting in a smaller heat capacity in the reformer, improved reformer start-up and responsiveness, and improved durability of the reformer and heat exchanger Will improve.

  As a result of earnestly searching for the relationship between the amount of heat input and the reaction rate in the reforming reaction of the hydrocarbon fuel, the present inventor has found that there is a relationship as shown in FIG. That is, the relationship between the steam reforming (SR) reaction rate and the methane production (methanation) reaction and the amount of heat input to the reaction system is shown in FIG. It gradually increases with the region (1) with a small amount of heat, the region (2) in the amount of heat and the region (3) with a large amount of heat. On the other hand, the methanation reaction is relatively suppressed in the region (1) with a small amount of heat and the region (3) with a large amount of heat, but the methanation reaction easily proceeds in the region (2) in the amount of heat.

  Therefore, from the relationship between the SR reaction and the methanation reaction, the methanation reaction can be suppressed if the amount of heat is input so as to minimize the region (2). On the other hand, the SR reaction does not proceed only in the region (1), and only in the region (3), the temperature of the reforming system becomes high, resulting in problems such as durability of the reforming portion and thermal deterioration of the catalyst. As a result of the increase in the outlet temperature of the reformer, the amount of heat applied to the heat exchanger installed on the downstream side of the reformer increases, and the durability of the heat exchanger becomes a problem. The problem that the capacity | capacitance of a heat exchanger becomes large arises.

Therefore, the present inventors perform reforming of the hydrocarbon-based fuel at a lower temperature and higher efficiency by distributing the region (1) and the region (3) in a well-balanced manner, and further suppress the production of methane. As a method, it has been found that the method shown in FIG. 2 is appropriate.
That is, a heating region is locally provided in the middle of the reactor in the gas flow direction of the reformer. This heating region gives an input heat amount corresponding to the region (3) in FIG. The heating region may be set in the middle of the reactor length (gas length direction) of the reformer, but if it is in the vicinity of the outlet of the reformer, the outlet temperature of the reformer may increase. Therefore, it is desirable to set the heating region inside the reformer except for the vicinity of the outlet of the reformer.

  FIG. 3 is a conceptual perspective view showing a preferred embodiment of the hydrocarbon reformer of the present invention. In FIG. 3, the reformed gas circulation layer 10 to which the hydrocarbon-based fuel to be reformed is supplied and the combustion gas circulation layer 12 to which the fuel gas for heating the reformed gas is supplied are alternately stacked. ing. A hydrocarbon such as gasoline and steam are supplied to the reformed gas circulation layer 10. Fuel gas and air for burning the gas are introduced into the combustion gas circulation layer 12 adjacent to each reformed gas circulation layer 10.

  In the middle of the combustion gas circulation layer 12, an oxidation catalyst layer 14 is provided in a direction substantially orthogonal to the reformed gas flow in the reformed gas circulation layer 10. A catalyst for promoting the reforming reaction is supported on the reformed gas circulation layer 10. As such a catalyst, a copper-zinc base metal catalyst, a platinum catalyst, or the like can be used. As the carrier for supporting these catalysts, porous ceramics such as alumina and titania can be used.

  In the fuel gas circulation layer 12, an oxidation catalyst for promoting combustion oxidation of the fuel gas is supported on the carrier. Examples of the carrier include porous ceramics such as alumina and titania. Examples of the oxidation catalyst include noble metal catalysts such as Pt and Pd, and copper-zinc base noble metal catalysts. From the viewpoint of local oxidation, noble metals such as Pt and Pd are particularly highly reactive. A catalyst is preferred.

  FIG. 4 is an explanatory diagram showing a heat transfer relationship between the reformed gas circulation layer 10 and the combustion gas circulation layer 12 in the present invention. In FIG. 4, when fuel gas and air are introduced from the outside into the oxidation catalyst layer 14 provided in the middle of the combustion gas circulation layer 12, the fuel gas burns in the oxidation catalyst layer 14, and heat is rapidly generated in this portion. Will occur. This heat is transferred to the reformed gas circulation layer 10 adjacent to the combustion gas circulation layer 12. The steam reforming reaction is an endothermic reaction that generates hydrogen from fuel and steam. Therefore, in the reformed gas circulation layer 10, the steam reforming reaction proceeds by receiving heat from the oxidation catalyst layer 14, and the gas temperature gradually decreases on the upstream side of the reformed gas flow due to the endothermic reaction.

  As described above, the vicinity of the reformed gas circulation layer adjacent to the site of the oxidation catalyst layer 14 is locally heated, so that it becomes a region corresponding to the region (3) having a large amount of heat in FIG. 1, and the SR reaction proceeds. In addition, the methanation reaction is suppressed. Therefore, it is possible to increase the efficiency of the reforming reaction while suppressing the generation of methane. Then, the reformed gas is introduced into the endothermic reaction of the steam reforming reaction and the reformed gas and the combustion gas circulation layer 12 and heat exchange between the low-temperature fuel gas and the air before catalytic combustion is performed in a state where the temperature is lowered It is introduced from the reformer to the downstream equipment.

  The hydrogen rich gas obtained through the reformed gas circulation layer 12 is heat-exchanged by a heat exchanger and then introduced into the CO separation unit. The CO separation unit includes a shift reaction unit and a hydrogen separation unit. The shift reaction unit generates hydrogen from carbon monoxide contained in the hydrogen-rich gas and water vapor supplied from the outside of the shift reaction unit. Of these hydrogen-containing gases, only hydrogen is selectively separated in a hydrogen separation section having a hydrogen separation membrane, and this hydrogen is supplied to a fuel cell or the like. Further, the obtained hydrogen can be supplied to a hydrogen consumption system other than the fuel cell. Note that the CO separation unit can be omitted depending on the component ratio of the hydrogen-rich gas and the equipment to which the hydrogen-rich gas is supplied.

  Examples of equipment installed on the downstream side of the reformer include a heat exchanger, a hydrogen separation membrane, and a CO shift reactor. In these equipment, the operating temperature is 200 ° C. to 600 ° C. Preferably, it is around 500 ° C. According to the operation method of the reformer provided with the local heating region in the present invention described above, (1) the reformed gas discharged from the reformer has a low temperature of about 500 ° C. Since it is almost equal to the operating temperature of the flow-side equipment, it is possible to eliminate the need for a heat exchanger or to reduce the size of the heat exchanger. Is about 650 ° C., and the temperature difference between the reformer and the downstream apparatus is reduced, so that the durability of the reformer and the downstream apparatus is improved. (3) Overall catalyst in the reformer The temperature can be reduced and sintering of the catalyst components such as precious metals can be suppressed, so that the thermal deterioration of the catalyst can be suppressed. (4) The temperature drop of the reformer and the need for a heat exchanger can be eliminated. As a result, the capacity of the reforming unit is reduced, and the start-up and response in the reforming unit are improved. To.

  In the above-described embodiment, gasoline has been described as an example of the hydrocarbon fuel, but oxygen-containing hydrocarbon fuels such as alcohol, and gaseous hydrocarbons such as LPG and LNG can also be used. . In addition, an example in which the hydrocarbon-based fuel and steam are supplied to the reformed gas circulation layer to perform a steam reforming reaction has been shown. It may be a case where air and steam are supplied to perform the partial oxidation reaction and the steam reforming reaction at the same time.

  If the arrangement state of the oxidation catalyst layer in the reformer is in the middle of the reformed gas flow direction of the reformed gas circulation layer, at least the amount of heat in the reformed gas circulation layer adjacent to the oxidation catalyst layer increases, The reaction (SR reaction) proceeds. However, in order to maintain the temperature of the reformed gas at the outlet of the reformer within a predetermined range, the reformed gas may be changed depending on whether the steam reforming reaction or the steam reforming reaction and the partial oxidation reaction are performed simultaneously. Although the temperature is different, the position where the oxidation catalyst layer is arranged is preferably a position away from the outlet side of the reformer. The size of the oxidation catalyst layer varies depending on the type of the oxidation catalyst, the hydrocarbon-based fuel, and the like, but may be a size sufficient for the steam reforming reaction to proceed sufficiently.

Examples of the present invention will be described below.
(Example)
A combustion gas circulation layer in which an oxidation catalyst having an oxidation catalyst (Pt) supported on a carrier (alumina) is provided at substantially the center in a direction perpendicular to the gas flow direction of the combustion gas circulation layer (thickness 10 mm, length 100 mm, width 100 mm); A reformer as shown in FIG. 3 was manufactured by alternately laminating reformed gas circulation layers having a reforming catalyst, which are approximately the same size as the combustion gas circulation layer (comparative example).
A combustion gas circulation layer (thickness 10 mm, length 100 mm, width 100 mm) in which an oxidation catalyst having an oxidation catalyst (Pt) supported on a carrier (alumina) is uniformly provided on the entire surface, and approximately the same size as this combustion gas circulation layer A reformer was produced in which reformed gas circulation layers having reforming catalysts were alternately stacked.

Gasoline and water vapor were supplied to the reformed gas circulation layer of these reformers, and gasoline and air were supplied as fuel gas to the combustion gas circulation layer.
As a result of examining the heating distribution in these reformers, as shown in FIG. 5, in the case of the comparative example (uniform heating method), the heating distribution is uniform in the catalyst length direction. In the case of the superheating method), the heating distribution had a peak shape in the middle of the catalyst length direction.

Further, the examples and comparative examples, the temperature of the reformed gas in the reformer outlet, CO _X, conversion to CH _4, CH ₄ concentration, the results of measurement of the reforming efficiency, shown in Table 1. In Table 1,
<CO _X, conversion to CH _4>
X- FUEL: Number of moles of fuel in the input gas (mol / s)
_C- FUEL: Carbon number of fuel
_X- CO: Number of moles of CO in reformed gas (mol / s)
_X- CO ² : Number of moles of CO ² in the reformed gas (mol / s)
_X- CH ⁴ : CH ⁴ moles in the reformed gas (mol / s)
_X- H ² : Number of moles of H ² in reformed gas (mol / s)
LHV _- FUEL: Lower heating value of fuel (J / mol)
LHV _- H ² : Lower heating value of H ² (J / mol)
The conversion and reforming efficiency were calculated based on the following formula.
Conversion ^{_{= (X- CO + X- CO 2}} + X- CH 4) / (X- FUEL × C- FUEL) × 100%
Reforming efficiency = ( _X− CO + _X− H ² ) × LHV ₋ H ² / ( _X− FUEL × LHV ₋ FUEL) × 100%
Note that CO is also efficiently added as hydrogen here, assuming that the CO shift unit converts CO to H ² .

  From the results of Table 1, in the example (local heating method), the temperature of the reformed gas at the outlet of the reformer is lower than that of the comparative example (uniform heating method), the concentration of methane in the reformed gas is low, and It shows that the reforming efficiency is high.

It is a graph which shows the relationship between the heat input to the reaction system in a reformer, and reaction rate. It is a graph which shows the relationship between the length of the reactor in the reformer for showing in principle the hydrocarbon reforming reaction method of this invention, and the amount of heat input into the reaction system. It is a schematic block diagram of the principal part which shows one Embodiment of the reformer of this invention. It is a graph which shows the temperature relationship in the reformed gas distribution layer and fuel gas distribution layer in the reformer of FIG. It is a graph which compares and shows the heating distribution of this invention (local heating type) and the conventional (uniform heating type) in a reformer. It is explanatory drawing which shows the flow of the hydrogen rich gas from a reformer.

Explanation of symbols

10 Reformed Gas Flow Layer 12 Combustion Gas Flow Layer 14 Oxidation Catalyst Layer

Claims (4)

  A reformer in which a reformed gas circulation layer to which a hydrocarbon-based fuel is supplied and a combustion gas circulation layer to which a fuel gas is supplied are alternately stacked, in the middle of the gas flow direction in the reformed gas circulation layer A reformer characterized in that a portion to be locally heated is provided.   The site of locally heating in the middle of the gas flow direction in the reformed gas circulation layer is provided with an oxidation catalyst layer in the middle of the gas flow direction of the combustion gas circulation layer to which fuel gas is supplied. Item 2. The reformer according to Item 1.   An operation method of a reformer in which a reformed gas circulation layer to which a hydrocarbon-based fuel is supplied and a combustion gas circulation layer to which a fuel gas is supplied are alternately stacked, the gas flow in the reformed gas circulation layer An operation method of a reformer characterized by locally heating in the middle of a direction. The oxidation catalyst layer is provided in the middle of the gas flow direction of the combustion gas circulation layer to which the fuel gas is supplied, and the middle of the gas flow direction in the reformed gas circulation layer is locally heated. The operation method of the reformer according to 3.

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